In Vivo Imaging of Near‐Membrane Calcium Ions with Two‐Photon Probes

Abstract

We report a two-photon (TP) probe (ACaLN) for near-membrane Ca(2+) that shows a 13-fold TP excited fluorescence (TPEF) enhancement in response to Ca(2+), dissociation constants (K(d)(TP)) of (1.9±0.2) μM, pH-insensitivity at the biologically relevant pH, and can detect near-membrane Ca(2+) in live cells for more than 1500 s and in living tissues at 120 μm depth without interference from other metal ions. Comparison with existing probes provides a useful strategy for the design of efficient TP probes for the near-membrane metal ions.